View Single Post
  #4  
Old 12-13-2011, 07:32 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 10,699
Default

Quote:
Originally Posted by Lars View Post
And the performance difference would be related to what... the oil spray nozzles applied to the pistons on the angle valve engines, which are lacking on the parallel valve engines? Or something else?
That's the common belief. Piston squirters certainly increase the percentage of waste heat being shed through the oil cooler.

I've also heard it argued that the angle valve cylinders have more fins or more effective fins. Anybody care to estimate the relative fin areas for the 360 parallel and angle valve cylinders? The charts suggest the 360-size angle cylinders do not have more passage area between the fins; the mass flows are the same (a little over 1.5 lbs/sec) for the same pressure drop and altitude. I suppose they could have more fins and narrower passages.

Quote:
Originally Posted by Alan Carroll View Post
If I'm reading these charts correctly the parallel valve engines need something like 25-30% more cooling air to achieve the same CHT as the parallel valve?
For equal CHT at 60F OAT I read required mass flow as:

320 1.45 lbs/sec
360 1.8
IO360 1.4
IO390 1.45

Quote:
On the other hand it would seem that the total heat production for the angle valve engine must be as great or greater than the parallel valve, assuming the same combustion temperature.
Yep. Two choices; the additional waste heat must leave town via the oil system, or by heating the cooling air to a higher temperature. One, the other, or both...right now I don't know.
__________________
Dan Horton
RV-8 SS
Barrett IO-390

Last edited by DanH : 12-13-2011 at 07:42 AM.
Reply With Quote